1. Field of the Invention
This invention relates to insulating-material bodies being a laminate of a plurality of sheets and, in case, a surface layer, at least one of said sheets or the surface layer, containing therewithin finely and essentially statistically distributed particles of metals of Group VIII or Ib of the Periodic Table of the Elements and to methods for producing such insulating bodies by introducing into a resinous impregnating solution of a prepeg or into the adhesive of a surface layer a solution of a reduicable metal compound of a metal of Group VIII or Ib of the Periodic Table, said metal compound distributed in the resin or adhesive being reduced to finely distributed metal particles when a lay-up of sheets and, in case, a surface layer are cured under heat and pressure to form the laminate. Where the insulating-material body contains reducible metals in the form of compounds, e.g. salts of Group VIII or Ib of the Periodic Table of the Elements the metal itself is formed in fine distribution when the resin bond laminate is produced by exposure to heat and pressure.
This invention is particularly concerned with the production of insulating-material bodies for use in the production of printed circuits for circuit boards with wholly or partially metallized surfaces, and in particular to insulating-material bodies with perforations whose inner walls are provided with a metal coating, which is deposed on the surfaces of the insulating bodies by the catalytical activity of said metal particles being exposed in the outer surface and inner walls of the insulating bodies.
2. Discussion of the Prior Art
It is known to treat the surfaces of insulating areas with solutions of reducible metals followed by a solution of reducing agents, the so formed reduced metal germs permit conductive patterns of printed corcuits to be applied in numerous steps. Improved insulating-material bodies are obtained, according to the proposals of German Offenlengungsschrift DOS No. 26 12 637, German Pat. No. 16 96 602 and German Auslegeschrift DAS No. 16 96 604, by adding catalytically active fillers to the resin mixture used to produce the insulating material. The catalytically active filler exposed at the surfaces and at the inner walls of the perforations brings about deposition of a metal coating of the insulating-material substrate from precipitating metal baths without the use of electric current.
These catalytically active fillers must be prepared from special fillers of a particular particle size in several separate operations involving the deposition of metal compound solutions, reducing the metal compounds to metal particles and drying of the fillers. Moreover, the introduction of the fillers into the resin solutions and their handling require special procedures. Yet there is no assurance that the fillers will be uniformly dispersed in the insulation material since even filler particles of small size are not uniformly dispersed in the impregnating solution and settle out.
The so formed insulating-material bodies having catalytically active metal particles inside and ready for forming metal coatings from a metal salt bath on parts or the total of their surface, clearly have deciseive disadvantages and problems not being dissolved by the art: when surfaces of ready preformed insulation bodies are surface treated with metal solutions, only such parts near the surface will contain the catalytically active metal germs, while the numerous holes and and fine borings of an electrical circuit have not enough or no metal germs, and when metal germs deposited on fillers divided in the resins, the filler-bond metal germs are not finely enough divided in the resin as even finely derived filler bodies are too big for this purpose and additionally, the separate production of filler-bond metal germs and dispersing then in a resin solution is rather costly.